JP2002350843A - Color filter for transflective liquid crystal display device and method of manufacturing the same - Google Patents

Abstract

[PROBLEMS] To provide a color filter for a transflective liquid crystal display device capable of eliminating a color difference between a reflective display and a transmissive display without increasing the number of manufacturing steps and capable of supporting both displays, and a method of manufacturing the same. thing. A cross section of one pixel of a color filter in a short side direction is a convex lens shape, the maximum thickness is 1.5 to 2.5 times the average film thickness, and the vicinity of a central portion is a transmission region. And a portion other than the vicinity of the center portion is defined as a reflection region. The pattern 22 is formed of a photosensitive color resist having a thermal reflow property, and is formed into a convex lens shape by thermal reflow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color filter for a liquid crystal display, and more particularly to a color filter for a transflective liquid crystal display having a transmissive display and a reflective display.

[0002]

2. Description of the Related Art A liquid crystal display device generally comprises a pair of opposing electrode substrates on which a polarizing film and a transparent electrode are provided, respectively, and a liquid crystal material sealed between the electrode substrates. . Further, in a color liquid crystal display device that displays a color image, a color filter for coloring light is provided on one of the pair of electrode substrates.

[0003] As a liquid crystal display device, the back or side surface of an electrode substrate located on the back side (of the paired electrode substrates, the electrode substrate located on the opposite side to the observer, hereinafter referred to as the back electrode substrate). A backlight-type or light-guide-type transmissive liquid crystal display device with a built-in lamp, in which a light source (lamp) is disposed and a screen is displayed by light emitted from the light source, is widely used. In a transmissive liquid crystal display device, it is common to provide a color filter for coloring transmitted light from a light source at a portion close to a liquid crystal material to perform color display.

FIG. 7 shows an example of a transmission type liquid crystal display device. A transparent substrate (71a), a transparent electrode (77), a liquid crystal material (74), a transparent electrode (75), a color filter (7
6), composed of a transparent substrate (71b), the light from the light source (lamp) (79) on the back is controlled by the liquid crystal substance (74) and is emitted to the observer side as transmitted light (L3). .

Conventionally, liquid crystal display devices have been expected to be used for portable display devices such as mobile devices, taking advantage of their features of low power consumption and light weight. However, in the transmissive liquid crystal display device with a built-in lamp, the power consumption of the light source is so large that the battery cannot be used for a long time, and the advantages inherent to the liquid crystal display device cannot be fully utilized.

For this reason, a reflection type liquid crystal display device has been proposed. The reflection type liquid crystal display device is preferable in this point because there is no power consumption for the light source. FIG. 6 is an explanatory view of a main part of a conventional reflection type liquid crystal display device. As shown in FIG. 6, the reflection type liquid crystal display device does not have a lamp for utilizing external light. TFT (thin film transistor) on a transparent substrate (61a) constituting the back electrode substrate
An array is formed (not shown). Next, an insulating film (not shown) having an uneven surface for light scattering is formed on the TFT (thin film transistor) array, and a reflective electrode (such as aluminum) is formed in a region on the insulating film corresponding to each pixel. 67) are laminated.

Here, the TFT (thin film transistor) array and the reflection electrode (67) are electrically connected by a via hole, and the transparent electrode (6) formed on the observer side electrode substrate.
The liquid crystal material (64) sandwiched between the electrodes 5) and the reflective electrode (67) is driven. The observer-side substrate has a color filter (66) for coloring the incident light (L1) incident from the outside and the reflected light (L2) reflected by the reflective electrode (67) and visually recognized by an external observer. And a transparent electrode (65) formed on a transparent substrate (61b).

However, a reflective liquid crystal display device has better visibility than a transmissive type in a bright room or outdoors in the daytime,
Since external light is used, there is a drawback that the display device does not function in a dark room or at night without external light. For this reason, a display device incorporating both the low power consumption of the reflection type liquid crystal display device and the good visibility of the transmission type liquid crystal display device in a dark room is disclosed in, for example, Japanese Patent Application No. 9-2091.
As seen in the technology of No. 56, development of a transflective liquid crystal display device in which an opening is provided in a part of a reflective electrode and display can be performed in both reflective display and transmissive display is in progress.

FIG. 8 is a sectional view of an example of a transflective liquid crystal display device, and FIG. 9 is a plan view of one pixel thereof. FIG.
As shown in FIG. 9, for example, an opening (88) is provided at the center of the reflective electrode (87) of the pixel, and in a dark environment, a light source (lamp) (89) is turned on to transmit light from the lamp. The visibility is ensured by using (L4). However, in the case of the transflective liquid crystal display device, there is a disadvantage that the color tone in the color display is greatly changed between the case of transmission using a light source (lamp, transmitted light) and the case of reflection using external light.

That is, in a reflection type liquid crystal display device as shown in FIG. 6, which schematically shows a reflection type liquid crystal display device, external light (L1) passes through a color filter (66) twice.
On the other hand, as shown in FIG. 7, in the transmission type liquid crystal display device, the transmitted light (L3) from the lamp only passes through the color filter (76) once. For this reason, when the color filters for the reflective display and the color filters for the transmissive display have the same thickness, and the display color is matched to that for the reflective display, there is a problem that the display color becomes thin in the case of the transmissive type. The reason is that in the case of the reflective display, the thickness (T5) of the color filter substantially doubles as compared with the case of the transmissive display.

In order to match the colors of the reflective display and the transmissive display, for example, as shown in FIG.
The thickness (T8) of the color filter (56) of the reflection region (Re) is 2 times the thickness (T4) of the color filter (56) of the reflection region (Re).
Attempts have been made to double. However, if the thickness of the color filter is changed separately for transmissive display and reflective display,
There is a disadvantage that the manufacturing process of the color filter becomes extremely complicated. For example, in the related art, three processes of three colors of R, G, and B are conventionally required, and three manufacturing processes of three colors of R, G, and B in the transmission region and three manufacturing processes of three colors of R, G, and B in the reflection region are performed. And a total of six steps are required.

[0012]

An object of the present invention is to provide a color filter for a transflective liquid crystal display device capable of eliminating a color difference between a reflective display and a transmissive display without increasing the number of manufacturing steps of the color filter and capable of coping with both displays. And a method for manufacturing the same.

[0013]

According to the present invention, there is provided a color filter used in a transflective liquid crystal display device having a transmissive area and a reflective area in one pixel, wherein the cross-sectional shape of one pixel of the color filter in the short side direction is as follows. The central portion is a convex lens shape having a maximum thickness, the maximum thickness has a thickness of 1.5 to 2.5 times the average thickness of the color filter, the vicinity of the center portion as a transmission region, A color filter for a transflective liquid crystal display device, characterized in that a portion other than the vicinity of a central portion is a reflection region.

Further, the present invention is a color filter for a transflective liquid crystal display device, wherein a light scattering film is provided on the color filter for a transflective liquid crystal display device according to the above invention.

The present invention also relates to a method of manufacturing a color filter used in a transflective liquid crystal display device having a transmissive area and a reflective area in one pixel. 1) A photosensitive color resist having a thermal reflow property is formed on a substrate. Coating, 2) forming a pattern corresponding to one pixel by exposure and development, 3) heat reflowing the pattern by heating on the hardened film,
The maximum thickness of the central portion of the pattern has a thickness of 1.5 to 2.5 times the average thickness, the cross-sectional shape in the short side direction is formed into a convex lens shape, and the vicinity of the central portion is a transmission region, A method of manufacturing a color filter for a transflective liquid crystal display device, characterized by manufacturing a color filter having a portion other than the vicinity of a central portion as a reflection region.

Further, according to the present invention, in the method for producing a color filter for a transflective liquid crystal display device according to the present invention, the pattern is thermally reflowed by heating in the above 3) hard film, and the center of the pattern is formed. The maximum thickness is 1.5 of the average thickness
A method of manufacturing a color filter for a transflective liquid crystal display device, comprising forming a light scattering film after forming a cross-sectional shape in the short side direction having a thickness of 2 to 2.5 times into a convex lens shape. It is.

[0017]

Embodiments of the present invention will be described below in detail. FIG. 1 is a cross-sectional view of a transflective liquid crystal display device using one embodiment of a color filter for a transflective liquid crystal display device according to the present invention. As shown in FIG. 1, this transflective liquid crystal display device includes a transparent substrate (11b) such as a glass or plastic film, a color filter (16) for a transflective liquid crystal display device according to the present invention, and a light scattering film (13). , A transparent electrode (15), a liquid crystal substance (14), an opening (18), a reflective electrode (17), and a transparent substrate (11a).

The transparent substrate (11b) is used as an observer-side substrate, but the opposing back-side substrate is not limited to a transparent substrate (11a) such as a glass or plastic film, but may be formed of an optical functional film such as a polarizing film or a retardation film. Substrate may be used. Generally, a thin film of an alloy such as aluminum or silver is formed as a reflective electrode (17) on the surface of the transparent substrate (11a) in contact with the liquid crystal substance (14). Many area portions of the reflective electrode (17) are used as reflective areas in reflective display using external light.
An opening (18) (portion where no alloy thin film is formed) is provided at the center of the reflective electrode to serve as a transmission area, and in a dark environment, light transmitted from a built-in lamp arranged on the back side is used as a backlight in a dark environment. .

In the color filter (16) for a transflective liquid crystal display device according to the present invention shown in FIG. 1, the cross-sectional shape of one pixel in the short side direction is a convex lens shape having a maximum thickness at the central portion. The thickness is 1.5 to 2.5 times the average thickness of the color filter, and the vicinity of the center corresponds to the transmission region, and the portion other than the vicinity of the center corresponds to the reflection region. Therefore, it is possible to adjust the color difference of the liquid crystal display device between the transmissive display and the reflective display, and to eliminate the color difference.

The transflective type liquid crystal display device is used for applications that require brightness by placing importance on reflection, or for long-term use (energy saving) as a portable terminal, and complementing reflection display by placing importance on transmission display. The application can be divided into two categories, i.e., the use of the color filter, and it is preferable to adjust the film thickness and the color density of the color filter in the transmission region according to this category. That is, when importance is placed on brightness and energy saving, it is desirable to make the thickness of the central portion of the color filter in the transmissive region 1.5 to 2.5 times thicker at the expense of the saturation of transmissive display. Also, when importance is placed on the saturation, the thickness of the central portion is increased by a factor of 2.5 in order to eliminate light leakage from the thin film thickness portion (slightly away from the central portion) of the color filter in the transmission region. It is desirable to increase the thickness. In the transflective liquid crystal display device, it is necessary to adjust the transmittance of the color filter depending on the usage mode.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail. <Embodiment 1> FIGS. 2 to 4 are explanatory views of a process of manufacturing a color filter for a transflective liquid crystal display device according to the present invention.
As shown in FIG. 2, using a photosensitive resist in which a red (R) pigment is dispersed in an acrylic resin having a thermal reflow property, the first color (R) pattern (22) is reduced to 0 by a known photolithography technique. It was formed by exposing and developing on a transparent substrate (21) made of 0.7 mm thick glass (FIG. 2).

Then, the pattern (2)
2) is thermally reflowed so that the first color filter (1)
6) (Red (R)) (FIG. 3). The second color filter (16) (green (G)) and the third color filter (16) (green (B)) were formed in the same process. Further, as shown in FIG. 4, a light scattering film (13) was formed by coating. For the formation of the light scattering film, a mixed resin liquid obtained by dissolving a fluorine-based acrylic resin having a low refractive index (refractive index of 1.44) into which a fluorine group was introduced and an acrylic resin having a refractive index of 1.55 in an organic solvent was used. . In the mixed resin liquid, the low-refractive-index resin and the high-refractive-index resin were phase-separated at the time of drying after being applied on a color filter, so that light scattering properties could be imparted.

The color filter (16) had a maximum thickness Tt of 2 μm in a central region (a region opposed to the opening (18)) as a transmission region, and an average film thickness of 0.9 μm. The transparent electrode 15 was formed on the light scattering film. The shape of the color filter and the maximum film thickness Tt can be adjusted by appropriately adjusting the thermal reflow properties of the color filter base resin and the heat treatment (hard film) conditions.

The adjustment of the softening point of the monomer of the photosensitive resist, the polymer, the reflow temperature, and the curing agent,
The shape of the color filter can be adjusted. Also,
By devising the planar shape of the color filter, it is possible to provide auxiliary light scattering depending on the viewing angle. In addition, it is possible to provide a light condensing effect by making the color filter a convex lens shape, and to brighten the display. In this case, it is desirable that the refractive index of the photosensitive resist be lower than the refractive index of the scattering film.

[0025]

According to the present invention, the cross-sectional shape of one pixel of the color filter in the short side direction is a convex lens shape having the maximum thickness at the center thereof, and the maximum thickness is one of the average film thickness of the color filter. Since it is a color filter for a transflective liquid crystal display device having a thickness of 0.5 to 2.5 times, a central area as a transmissive area, and a part other than the central area as a reflective area, a color filter is manufactured. A color filter for a transflective liquid crystal display device that can deal with both displays by eliminating the color difference between the reflective display and the transmissive display without increasing the number of steps.
Further, there is an additional effect that the display closer to the center becomes brighter due to the light condensing action by the convex lens shape.

Further, the present invention is a color filter for a transflective liquid crystal display device in which a light scattering film is disposed on the color filter for a transflective liquid crystal display device, so that the color difference between the reflective display and the transmissive display can be reduced. There is a merit that can be adjusted. In other words, the thickness of the light scattering film is different between the transmission region and the reflection region, and the formation state of the scattering particles in the light scattering film can be adjusted for each region. Can be matched to the display request. For example, the effect of finely adjusting the degree of light scattering in the lateral (left / right) direction and the vertical direction from the observer, or the effect of suppressing light scattering in the transmission region and increasing the light scattering in the reflection region. is there.

According to the present invention, a pattern is formed from a photosensitive color resist having a thermal reflow property, and a thermal reflow is performed to form a convex lens shape. Since this is a method of manufacturing a color filter for a transflective liquid crystal display device that manufactures a color filter as an area, the color difference between the reflective display and the transmissive display can be eliminated without increasing the number of steps of manufacturing the color filter, and the method is compatible with both displays. A method of manufacturing a color filter for a transflective liquid crystal display device that can be used.

Further, according to the present invention, in the method of manufacturing a color filter for a transflective liquid crystal display device, a light scattering film is applied after forming a pattern into a convex lens shape. A method of manufacturing a color filter for a transflective liquid crystal display device that can be finely adjusted is provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a transflective liquid crystal display device using one embodiment of a color filter for a transflective liquid crystal display device according to the present invention.

FIG. 2 is an explanatory diagram of a manufacturing process of a color filter for a transflective liquid crystal display device according to the present invention.

FIG. 3 is an explanatory view of a process of manufacturing a color filter for a transflective liquid crystal display device according to the present invention.

FIG. 4 is an explanatory diagram of a manufacturing process of a color filter for a transflective liquid crystal display device according to the present invention.

FIG. 5 is an explanatory diagram of an attempt to match colors of reflective display and transmissive display.

FIG. 6 is an explanatory diagram of a main part of a conventionally used reflective liquid crystal display device.

FIG. 7 is an explanatory diagram of an example of a transmission type liquid crystal display device.

FIG. 8 is a cross-sectional view of an example of a transflective liquid crystal display device.

9 is a plan view of one pixel of the transflective liquid crystal display device shown in FIG.

[Explanation of symbols]

11a, 11b, 21, 51a, 51b, 61a, 61
b, 71a, 71b, 81a, 81b ... transparent substrate 13, 83 ... light scattering film 14, 54, 64, 74, 84 ... liquid crystal material 15, 55, 65, 67, 75, 77, 85 ... transparent Electrode 16 Color filter for transflective liquid crystal display device according to the present invention 17, 57, 87 Reflective electrode 18, 88 Opening 22 Pattern 56, 66, 76, 86 Color filter 79, 89 ... Light source (lamp) L1... Incident light L2... Reflected light L3, L4... Transmitted light Tr...

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H048 BA43 BA45 BA48 BA66 BB02 BB07 BB10 BB44 2H091 FA02Y FA08X FA14Y FA29Y FA31Y FA41Z FC22 FD04 LA15 LA16

Claims (4)

[Claims] In a color filter used in a transflective liquid crystal display device having a transmissive region and a reflective region in one pixel, the cross-sectional shape in the short side direction of one pixel of the color filter has a maximum thickness at a central portion thereof. A convex lens shape, wherein the maximum thickness is 1.5 to 2.5 times the average thickness of the color filter.
A color filter for a transflective liquid crystal display device having a thickness twice as large, wherein a portion near the center portion is a transmission region and a portion other than the portion near the center portion is a reflection region. 2. A color filter for a transflective liquid crystal display device, wherein a light scattering film is provided on the color filter for a transflective liquid crystal display device according to claim 1. 3. A method of manufacturing a color filter for use in a transflective liquid crystal display device having a transmissive region and a reflective region in one pixel, comprising: 1) applying a photosensitive color resist having thermal reflow properties to a substrate; ) A pattern corresponding to one pixel is formed by exposure and development. 3) The pattern is thermally reflowed by heating the hardened film.
The maximum thickness of the central portion of the pattern has a thickness of 1.5 to 2.5 times the average thickness, the cross-sectional shape in the short side direction is formed into a convex lens shape, and the vicinity of the central portion is a transmission region, A method of manufacturing a color filter for a transflective liquid crystal display device, comprising manufacturing a color filter having a portion other than the vicinity of a central portion as a reflection region. 4. The pattern is thermally reflowed by heating in the above 3) hardened film, and the maximum thickness at the center of the pattern is 1.5 to 2.5 times the average film thickness. 4. The method for manufacturing a color filter for a transflective liquid crystal display device according to claim 3, wherein a light scattering film is applied after forming the cross-sectional shape in the short side direction into a convex lens shape.